Rotating calcining kilns are utilized for calcining various materials including so-called green coke. Particulate green coke is fed into one end of an inclined rotating generally cylindrical kiln, and burners near the discharge end of the kiln provide heat for transforming green coke into calcined coke as the coke moves through the calciner. In order to obtain uniformity in calcining, it is conventional to provide lifters (mixers) in at least part of the calciner interior. The calciner interior typically is lined with refractory material to protect the calciner shell from the high calcining temperature. Mixers comprised of reinforced refractory material are typically located in a pattern on the calciner interior. These mixers project into the kiln interior beyond the surface of the refractory lining and assist in the mixing and tumbling of the particulate material being calcined, resulting in a more uniformly calcined material than would be obtained in the absence of the mixers.
Mixers formed of refractory material are satisfactory up to a point, but over a period of several months to one or two years these mixers degrade by spalling and crumbling, resulting in reduced calcining efficiency between shutdowns for repair. In the past, when calciners have been shut down for scheduled maintenance, repair of refractory mixers has been required.